Telegraph alarm circuits



Oct. 23, 1934.

w. T. REA 1,977,776

TELEGRAPH ALARM CIRCUITS Filed Oct. 27. 1951 Fens/afar INVENTOR ATTORNEYPatented Oct. 23, 1934 PATENT TELEGRAPH ALARM omcurrs Wilton T. Rea,Flushing, N. Y., assignor to American Telephone and Telegraph Company, acorporation of New York Application October 27,

2 Claims.

This invention relates to telegraph systems f utilizing voice frequencyor carrier currents for transmission of signals and more particularlyrelates to improvements in alarm arrangements for such systems forindicating failure or undesirable variations in the output of thegenerating devices utilized to produce telegraph signaling currents.

In telegraph systems of the'voice frequency signaling type, thegenerator of the signaling currents is usually connected to a frequencyindicator circuit so that the characteristics of current may beobserved. The output of the generator will be connected to a branchedcircuit havingtwo paths, one including a filter and an amplifier and theother including a resistance net- 'work and amplifier. The platecircuits of the two amplifier tubes will be connected to a differentialm-illiammeter and thence to a common source of plate current. Relaymeans will be provided having opposing windings included in each platecircuit. The relay means and branched circuits would be so adjusted thatwhen the frequency of the generator output was of a desired value, thecurrents in the relay windings would oppose and neutralize each other.However, any variations in the frequency of the generator output beyonddesired limits would upset the balanced condition in the relay windingsand cause the relays to operate and give an alarm. The invention relatesto improvements in alarm arrangemen'ts of the above type. One of thefeatures of the invention consists in the provision of mmns for givingan alarm in the event of a total failure of the generator. A furtherfeature relates to improvements in looking arrangements for the alarmdevice. Further objects and features of the invention will appear morefully in the detailed description thereof hereinafter given.

The invention may be more fully understood from the followingdescription together with the accompanying drawing, in the figure ofwhich is a circuit diagram illustrating the preferred form of theinvention.

In the drawing is shown generator 1 of voice frequency currents to beutilized to transmit telegraph signals over the telegraph line 2. Afrequency indicator and alarm circuit would be associated with theoutput of the generator 1 by means of the transformer 3. This circuitwould comprise two branched paths. One path would include a low-passfilter 4 and a vacuum tube amplifier 6. The other path would include theresistance network 5 and the vacuum tube ampliiier 7. The plate circuit8 of tube 6 would 1931, Serial-No. 571,397

include the windings 9 of relay R1, the windings 2' 10 of relay R2 andthe windings of a differential milliam-meter 11. The plate circuit 16 oftube "7 would include the windings 17 of relay R1, windings 18 of relayR2 and the windings of 'a'-differ- R1 will opposeeach other and thewindings 10 and 18 will oppose each other. Hence, if the generator 1 isfunctioning properly neither of the relays R1 or R2 will be operated.Under such through biasing windings 19 and 20 to the ground 30 will holdthe armatures of relays R1 andR2-in the position shown. This willmaintain the auxiliary circuit for the alarm device 23' in an opencondition and the alarm device 23 will not/function. 7

If the frequency of the output of the generator 1 should vary beyonddesirable'limits, the current in the two plate circuits and in the relay'windings would not, in effect, neutralize each other.

For example, if the frequency of the output of the generator increasedbeyond desirable limits, relay R1 would operate and if the frequency ofthe output of the generator decreased beyond certain limits, the relayR2 would operate. The

operation of relay R1 would cause its armature to move to its left-handcontact and close the following circuit; from battery 27, contact ofswitch 29, conductor 31, armature and left-hand contact of relay R1,winding of alarm device 23, 1;.

contact and armature of alarm device 23 to ground. This would cause thedevice 23 to operate in an intermittent manner, such, for example, as abuzzer and give an alarm. When the relay R1 operates, the followinglocking circuit will be I closed therefor; from battery 27, contact ofswitch 29, conductor 31, armature and contact of relay R1, conductor 32,contact of switch 26 and through the holding windings 22 and 21 to theground 30. This will lock the relay 17 in the operated condition andcause the alarm device 23 to function until the alarm circuit is brokenby operating the switch 26. The operation of relay R2 would cause it tomove its armature to its right-hand contact and close a similaroperating circuit for the alarm V OFFICE;

cuits 8 and 16. The windings 9 and 17 of relay e conditions, currentfrom the battery '27 flowing device 23 and the circuit for the holdingwindings 21 and 22.

If the generator should fail completely, no current would flow in theoperating windings of relay R1 and R2 and current in the biasingwindings l9 and 20 would hold the armatures in the position shown, Thealarm device, 23 would not be operated by these relays. Accordingly, thearrangements of the invention provide in the common portion 12 of theplate circuits of the tubes the relay 13. This relay is normally heldoperated by the current in the plate circuits of the tubes 6 and '7. Ifthe generator output fails, the current in the plate circuits will failand relay 13 will release. This will close the following circuit; frombattery 27, contact of switch 29, conductor 33, armature and contact ofrelay 23, armature and contact of relay '13, conductor 32, winding ofalarm device 23 to ground. Accordingly, if the generator output failscompletely,

.thealarm device 23 will be operated by the release of relay 13.

Y If the fuse should burn out, the relay 13 would be released. In orderthat the releaseof ,therelay 13 for such a cause should not give analarm, the relay 24 is provided; The burning out of the fuse 25wouldalso release the irelay'24. Accordingly, the circuit for the alarmdevice 23 would be held open at the contact of relay 24 and the alarmdevice would not be operated by the release of relay 13. A switch 29 isprovided whereby the battery 27 may be disconnected from the alarmarrangements and the deemeddesirable, it is understood that it iscapable of embodiment in many and other widely varied forms withoutdeparting from the spirit of the invention as defined by the appendedclaims.

What is claimed is: V

1. In a telegraph system a generator of signaling frequencies, afrequency indicating circuit connected to the output of said generator,said -frequency indicating circuit comprising two branched cirouits,oneof said circuits including a low pass filter and a vacuum tubeamplifier, the other of said circuits including a resistance network anda Vacuum tube amplifier, individual plate circuits for said tubesconnected to a milliammeter, a common plate circuit for said tubesconnecting said milliammeter to a source of plate current, relays havingoperating windings in each of said individual plate circuits, biasingwindings and holding windings for said relays, said operating andbiasing windings of said relays being so adjusted that one of saidrelays will operate in response to an increase from the normal frequencyof said generator and the other of said relays will operate in responseto e decrease from the normal frequency of said generator, an auxiliarycircuit controlling an alarm device, said auxiliary circuit beingcompleted over the contacts of said relays, and means for completing acircuit for said holding windings over the contacts of said relays andsaid auxiliary circuit whereby said relays will remain permanentlylocked up until said circuit is opened.

2. In a telegraph system a generator of signaling frequencies, afrequency indicating circuit connected to the output of said generator,said frequency indicating circuit comprising two branched circuits, oneof said circuits including a low pass filter and a vacuum tubeamplifier, the other of said circuits including aresistance network anda vacuum tube amplifier, individual plate circuits for said tubesconnected to a milliammeter, a common plate circuit for said tubesconnecting said milliammeter to a source of plate current, relays havingoperatingwindingsin each of said individual platecircuits, biasing andholding windings for said relays, said operating and biasing windings ofsaid relays being so adjusted that one of said relays will operate inresponse to an increase from the normal frequency of said generator andthe other of said relays will operate in response to a decrease from thenormal frequency of said generator, an auxiliary circuit controlling analarm device, said auxiliary circuit being completed overthe contacts ofsaid relays, means for completing a circuit for said holding windingsover the contacts of said relays and said auxiliary circuit whereby saidrelays will remain permanently locked up until said circuit-is opened,and switching means for opening said lastv mentioned means. i

